Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631 QA, QC, and Data Verification

1
Mercury Collection and Analysis in Ambient and
Effluent Waters using EPA Method 1631QA, QC,
and Data Verification

• Judy Schofield
• DynCorp, Science and Engineering Group

Office of Water
SCC-99-004.ppt
2
Clean Techniques Review

• General requirements
• Clean sampling and storage procedures
• Clean sample handling procedures in field and lab
• Use of clean bench or a clean room
• Comprehensive QA/QC program
• Analysis of blanks, blanks, and more blanks
• Level of cleanliness needed may vary, depending
  on metal, target concentration, and sampling
  location

3
Blanks and Definitions Review

• Equipment Blank
• Bottle Blank - generated by filling a sample
  bottle with reagent water acidified to pH lt 2,
  allowing the bottle to stand for 24 hours, and
  analyzing the water
• Sampler Check Blank - generated at the lab by
  processing reagent water through the sampling
  equipment using the same procedures that will be
  used in the field, and collecting and analyzing
  the water
• Field Blank - generated by filling a large carboy
  with reagent water in the laboratory,
  transporting the container to the field,
  processing the reagent water through the entire
  sampling system, and analyzing the sample

4
Blanks and Definitions (cont.)

• Reagent Blank
• Determines Hg concentration in solutions of
  reagents
• Generated by adding all analytical reagents to
  previously purged reagent water in the bubbler

5
Blanks and Definitions (cont.)

• Analytical Batch
• A set of samples oxidized with the same batch of
  reagents, and analyzed during the same 12-hour
  shift.
• A batch may be from 1 to as many as 20 samples.

6
Method Detection Limit
Establishes ability to detect Hg
7
Initial Precision and Recovery
Establishes laboratory ability to generate
acceptable precision and recovery with the method
8
Reagent Blanks
Determine level of contamination in all
solutions of reagents
Test
Spike Amount
Minimum
Criteria
Frequency
Reagent Blanks
NA
Each new batch of reagents, and in triplicate
each month
25 pg
9
Equipment Blanks
Demonstrate the sample bottles are free
from contamination
Test
Spike Amount
Minimum
Criteria
Frequency
Bottle Blanks
NA
1 per cleaning batch
lt 0.5 ng/L or one- fifth Hg in associated sample
(s), whichever is greater
10
Equipment Blanks (cont.)
Demonstrate the sampling equipment is free
from contamination
Test
Spike Amount
Minimum
Criteria
Frequency
Sampler Check Blank
NA
1 following each cleaning batch
lt 0.5 ng/L or one- fifth Hg in associated sample
(s), whichever is greater
11
Field Blanks
Demonstrate acceptable levels of
contamination associated with sample collection,
handling, and transport
Test
Spike Amount
Minimum
Criteria
Frequency
Field Blanks
NA
10 from same site at same time
lt 0.5 ng/L or one- fifth Hg in associated sample
(s), whichever is greater
12
Ongoing Precision and Recovery
Demonstrate lab operations are in control (e.g.,
acceptable precision and recovery) within each
analytical batch
Test
Spike Amount
Minimum
Criteria
Frequency
Ongoing Precision and Recovery (OPR)
5 ng/L
Prior to and after analysis of each analytical
batch
Percent recovery 77 - 123
13
Matrix Spike/Matrix Spike Duplicate
Demonstrates the precision and accuracy of the
method and the sample matrix
Test
Spike Amount
Minimum
Criteria
Frequency
Matrix Spike/ Matrix Spike Duplicate (MS/MSD)
Compliance limit or 1-5x background, whichever
is greater
10 from a givensampling site or discharge
Percent recovery 71 - 125 Relative
Percent Difference 24
14
Blank Results

• Provide information about extent and nature of
  contamination
• Can be used to identify areas in need of future
  corrective action
• If desired, lab blank (e.g., reagent blank)
  contamination can be corrected through reanalysis
• Field and equipment blank contamination cannot
• Effect of blank contamination on data quality
  depends on extent of contamination, type of
  blank, and level of interest

15
Initial Precision and Recovery Results

• If desired, IPR failures can be corrected by
  reanalysis
• IPR series must be analyzed on the same
  instrument/detector system as field samples
• Failure to meet recovery criteria suggests lab
  may not be capable of producing accurate results
  with the method and its equipment/procedures
• Failure to meet standard deviation criterion
  suggests that the lab may not be capable of
  producing precise results with the method, its
  equipment, and its procedures

16
Ongoing Precision and Recovery Results

• If desired, OPR failures can be corrected by
  reanalysis
• In general, low OPR recoveries suggest a negative
  bias and high recoveries suggest a positive bias
  in field samples
• If OPRs were not analyzed at the required
  frequency, IPR, other OPR, and MS/MSD data may be
  used to assess data quality

17
Matrix Spike/Matrix Spike Duplicate Results

• If MS/MSD results fail to meet performance
  criteria but all other QC results are acceptable,
  method may not be appropriate for sample matrix
• Low spike recoveries suggest suppression from
  matrix
• High spike recoveries suggest enhancement from
  matrix
• Highly divergent recoveries indicate poor
  precision of the method with the matrix, and
  indicate that results for samples may be less
  precise than normal

18
Multiple QC Failures

• Examine QC in terms of type (e.g. laboratory,
  field or matrix QC) and direction
• Laboratory QC failures suggest that the
  analytical process may be responsible for field
  and/or matrix QC failures
• Multiple failures biased in the same direction
  can allow statements to be made about data
  quality with increased certainty
• Multiple failures with widely divergent impacts
  suggests data are too unreliable for many uses

19
Corrective Actions

• Should be taken as soon as is practical
• Examine trends (blanks, OPR, and MS/MSD control
  charts)
• Examine corrective actions taken by the lab and
  discuss (with lab and facility) additional
  measures that should be taken in the future
• Implement method improvements based on systematic
  trends identified within and across laboratories

20
Why Bother?

• Town of Falmouth, Maine conducted a study in 1998
• Historical Methods (Method 245.1)
• lt 220 ppt
• Method 1631
• 62.9 ppt
• Method 1631 with Method 1669
• 15.3 ppt

21
Sampling Tips

• Do not use sample containers that have not been
  demonstrated to be clean
• Either do not sample when its raining or prevent
  rainwater from falling into the sampling
  container
• Face upstream and upwind
• Avoid all sources of potential contamination
  including improperly cleaned equipment
  atmospheric inputs, and human contact
• Do not breathe into the sample bottle if you have
  mercury amalgam fillings in your teeth

22
Sampling Tips (cont.)

• Do not sample under or near a bridge or other
  metal structure. Metals can slough off of the
  structure and contaminate the sample.
• Do not sample when the wind could blow metal,
  debris, or dust particles into the sample bottle
• In general, the more blank samples that are
  collected and analyzed, the better the assessment
  of whether or not contamination has occurred.
  Method 1669 includes the minimum requirements for
  field and equipment blanks when collecting
  samples for mercury analysis at water quality
  criteria levels.